The oil industry seeks to communicate data, information and command signals along their drill holes over great distances. Enabling such communication is a great challenge due to the narrow cross-section of their pipes and the need to avoid blocking the flow of oil and other fluids that flow along the pipes. Generally, for underwater applications acoustic modems are used in worldwide subsea applications and they transmit data wirelessly through the water. However, such modems use acoustic transmitters and receivers that communicate in unobstructed water paths and they are not applicable to oil pipes having narrow passages and complex geometry. The limitation of conventional transducers that are used by existing acoustic modems results from their directivity that is not designed for travel in such constrained environments as an oil filled pipeline. Therefore, interferences, reflections and mode conversions take place that make the signal analysis of the communication algorithms an enormously complex task.
In conventional drilling practice, it is useful to obtain data from sensors that can be located at the advancing drill bit, or that can be located at positions in the well bore. Some of the kinds of apparatus and the data that are of interest include accelerometers and magnetometers to measure the inclination and azimuth of the wellbore as the well is being drilled so that the well can reach an intended location, information about the condition and operation of the drill bit, geological and chemical information about the formations and their compositions as the well passes through them, such as density, porosity, electrical resistivity data, magnetic resonance data, temperature and pressure data, gamma ray data, and the like.
In conventional drilling practice, the data can be communicated from the measurement device to a data collection an operation control station at the top of the well, or in some instances, to a similar station that is remote from the well itself. The communication methods that are conventionally used include mud pulse telemetry, electromagnetic telemetry and wired drill pipe systems.
In mud pulse telemetry, a valve is used to control the rate of flow of drilling mud, which can cause a change in pressure if the valve is activated over a short time interval. The pulses can be used to send data as digital pulsed signals, typically at data rates of tens of Hertz or lower. In addition, because the mud is also used as a drilling fluid, starting and stopping the flow of mud can disrupt the drilling action of the drill.
In electromagnetic telemetry, an electrical connection is made to the drill pipe itself, and the sensor or data generator is separated from the drill pipe by insulation. A second electrical contact is placed in the ground near the well. The two contacts form the two electrodes of a dipole antenna. The voltage difference between the two contacts represents a signal is the received signal that can be analyzed. This system can provide data rates of about 10 bits per second that are carried on very low frequency waves in the range of units to tens of Hertz. Electromagnetic telemetry has a limited depth capability, typically a few thousand feet.
In wired systems, an electrical connection such as a coax cable is provided to carry signals. While such systems can provide extremely high data rates, maintaining electrical connectivity can be an issue. One such system, called the IntelliSery wired pipe network by National Oilwell Varco of 7909 Parkwood Circle Dr., Houston, Tex. 77036, is reported to provide data rates upwards of 1 megabit per second, using induction coils to connect successive drill pipe sections.
It is known in the prior art to use ultrasonic phased arrays for medical imaging and for industrial non-destructive testing (NDT). Medical sonograms are commonly made with specialized multi-element transducers (phased arrays) and their accompanying hardware and software, and provide detailed cross-sectional pictures of internal organs. Phased array systems are also used in industrial settings to provide visualization in common ultrasonic tests that include weld inspection, bond testing, thickness profiling, and in-service crack detection.
Phased array probes typically consist of a transducer assembly with from 16 to as many as 256 small individual elements that can each be pulsed separately. These may be arranged in a strip (linear array), a ring (annular array), a circular matrix (circular array), or a more complex shape. As is the case with conventional transducers, phased array probes may be designed for direct contact use, as part of an angle beam assembly with a wedge, or for immersion use with sound coupling through a water path. Transducer frequencies are most commonly in the range from 2 MHz to 10 MHz. A phased array system will also include a sophisticated computer-based instrument that is capable of driving the multi-element probe, receiving and digitizing the returning echoes, and plotting that echo information in various standard formats. Unlike conventional flaw detectors, phased array systems can sweep a sound beam through a range of refracted angles or along a linear path, or dynamically focus at a number of different depths, thus increasing both flexibility and capability in inspection setups. Ultrasonic non-destructive test apparatus, components, software and control circuitry are available from a number of manufacturers, including Olympus Corporation, GE Measurement and Control, National Instruments, Sonatest, Inc., Marietta Nondestructive Testing Inc., X-R-I Testing Division of X-Ray Industries, and others.
Mulhauser, in 1931, obtained a German patent for using ultrasonic waves, using two transducers to detect flaws in solids.
Also known in the prior art is Firestone, U.S. Pat. No. 2,280,226, issued Apr. 21, 1942, which is said to disclose a device for detecting the presence of inhomogeneities of density or elasticity in materials.
Also known in the prior art is Firestone, U.S. Pat. No. 2,483,821, issued Oct. 4, 1949, which is said to disclose the inspection of materials by supersonic waves.
Also known in the prior art is Firestone, U.S. Pat. No. 2,625,035, issued Jan. 13, 1953, which is said to disclose electromechanical transducers. and particularly to a piezoelectric crystal apparatus for sending and receiving supersonic wave trains.
Also known in the prior art is Henry, U.S. Pat. No. 3,004,425, issued Oct. 17, 1961, which is said to disclose piezoelectric transducers, such as natural quartz, and particularly when utilized with instruments, such as the Ultrasonic Reflectoscope, which employ the pulse echo technique of ultrasonic materials inspection.
Also known in the prior art is Kossoff, U.S. Pat. No. 3,936,791, issued Feb. 3, 1976, which is said to disclose apparatus for ultrasonic examination of objects, particularly in medical diagnostic examination, comprised of a phased array transducer capable of focusing the beam of ultrasonic pulses in the longitudinal plane of the transducer, and focusing means to focus the dimensions of the beam normal to the longitudinal plane.
Also known in the prior art is Fox, U.S. Pat. No. 4,307,613, issued Dec. 29, 1981, which is said to disclose an array of transducer segments is arranged in columns, each of which has a multiplicity of segments. The segments are wired to permit excitation by one or the other of two opposite phases of high-frequency signal, and groups of segments can be excited with the same phase to approximate the shape of an annular-ring phase-reversal zone plate. By changing the groupings of the elements that are similarly excited, the position of the focal region produced by the zone plate is translated in lateral position. A ferrite-core transformer is conveniently employed for both phase splitting and addition of the echo signals received by the device.
Also known in the prior art is Smith et al., U.S. Pat. No. 4,890,268, issued Dec. 26, 1989, which is said to disclose a two-dimensional ultrasonic phase array is a rectilinear approximation to a circular aperture and is formed by a plurality of transducers, arranged substantially symmetrical about both a first (X) axis and a second (Y) axis and in a plurality of subarrays, each extended in a first direction (i.e. parallel to the scan axis X) for the length of a plurality of transducers determined for that subarray, but having a width of a single transducer extending in a second, orthogonal (the out-of-scan-plane, or Y) direction to facilitate dynamic focussing and/or dynamic apodization. Each subarray transducer is formed of a plurality of sheets (part of a 2-2 ceramic composite) all electrically connected in parallel by a transducer electrode applied to juxtaposed first ends of all the sheets in each transducer, while a common electrode connects the remaining ends of all sheets in each single X-coordinate line of the array.
Also known in the prior art is Han et al., U.S. Pat. No. 6,672,163, issued Jan. 6, 2004, which is said to disclose a method and apparatus for in-situ characterization of downhole fluids in a wellbore using ultrasonic acoustic signals. Measurements of the speed of sound, attenuation of the signal, and acoustic back-scattering are used to provide qualitative and quantitative data as to the composition, nature of solid particulates, compressibility, bubble point, and the oil/water ratio of the fluid. The tool generally comprises three sets of acoustic transducers mounted perpendicular to the direction of the flow. These transducers are capable of operating at different frequencies so that the spectrum of the acoustic signal can be optimized. The apparatus is capable of operating downhole to provide real time information as to conditions in the well.
Also known in the prior art is Alberty, U.S. Pat. No. 7,950,451, issued May 31, 2011, which is said to disclose methods and apparatus that combine a measurement of the physical velocity of material within the annulus of a well between the drill pipe and the wall of the well with a measurement of the area of the flow as determined from a measurement of distance between the drill pipe and the wall of the hole to determine the actual material volumetric flow rate. Changes in volumetric flow rate at one or more points along the well can be used to determine the occurrence and location of well dysfunctions. This knowledge can then be used to make decisions about treating well dysfunctions which will lead to more efficient use of drilling rig time.
There is a need for improved systems and methods for communication along bore holes.